The invention relates to an analysis apparatus for carrying out chemical analyses having a base member in which there is at least one channel, and having at least one functional element which is in fluid or gaseous connection with the channel.
In certain chemical analyses, a chemical sample that is able to flow is mixed with at least one reagent. The reagent reacts with the sample. A resulting reaction product, for example, a colour change, can then be detected by a detector.
To control the route from sample to reagent, U.S. Pat. No. 5,250,263 describes an analysis apparatus which essentially consists of a plurality of plates which are layered one above another in the manner of a stack. In each plate there are channels in the form of grooves in one of the surfaces, bores or openings which together form with a plate arranged thereover longitudinally or transversely running channels or reaction chambers. Furthermore, between individual plates there are provided membranes which can be acted on with compressed air through separate channels. These membranes then act as pumps. Valves which control the path of the fluids through the channels, for example, preventing a back flow, are also provided in some plates.
Such an apparatus can be of relatively compact construction, which has the advantageous effect that the necessary amounts of sample and reagent can be kept relatively small. Certain problems arise in handling, however, because the functional elements, for example, the valves and the pumps, are virtually inaccessible for maintenance. If such a functional element is defective, it is frequently the case that the entire apparatus must be exchanged. Moreover, in an experimental environment it is relatively difficult to undertake changes, for example, in respect of the characteristics of the pumps or the valves, because to do so the apparatus has to be virtually completely destroyed. Since there are a number of channels which are formed by successive bores, it is virtually impossible on assembly to repeat the same flow-through characteristics of these channels. Even small shifts in the individual plates relative to one another cause irregularities in the walls of these channels, which change the flow conditions there. Provided that only a few stages are affected, this can be tolerated. In the case of the described large number of superimposed plates, however, satisfactory reproducibility is very unlikely. In practice, components cannot be exchanged.